Alkali Flame Ionization Detector Research Articles

Characteristics of a novel alkali flame ionization detector as an air sensor for volatile organo-nitrogen compounds

A novel alkali flame ionization detector (AFID) is introduced and characterized for use as an air sensor (i.e., without chromatographic separation) for organo-nitrogen compounds. Using a planar channeled quartz design, a simple, lightweight architecture for the portable device is presented, which yields sensitive and selective response toward nitrogen-containing analytes. For instance, the AFID sensor offers a detection limit of 30 pg N/s and a selectivity for nitrogen response over carbon of nearly two orders of magnitude. Further, nitrogen response is linear over the 1000-fold range of concentrations investigated. Relative to a flame photometric detector (FPD) device also used in a sensor mode, the AFID is observed to provide 100 times greater S/N values for nitrogen analytes with a nitrogen-to-carbon selectivity that is about 15 times larger. When using the AFID and FPD sensors in tandem, it is found that the response ratio of the simultaneous signals generated by each produces characteristic values that more clearly identify the presence or absence of nitrogen in unknown analytes. The AFID sensor was used to detect organo-nitrogen analytes in several samples, and results indicate that it could be a useful approach for portable air sensing of nitrogen compounds.

Bioanalysis Through The Ages

Bioanalysis Through The Ages

Effect of paracetamol on amylobarbitone hydroxylation in man: a gas chromatographic method for simultaneous estimation of underivatized paracetamol and barbiturates.

A rapid and specific technique for the simultaneous gas chromatographic estimation of underivatized paracetamol and barbiturates using an alkali flame ionization detector is described which is suitable for both forensic and pharmacokinetic investigations. An improved method for estimation of 3-hydroxyamylobarbitone is also detailed. These techniques were used in an investigation of the effects of oral administration of 1 g paracetamol 8 hourly on the formation of 3-hydroxyamylobarbitone from a single oral dose of 200 mg sodium amylobarbitone. No significant changes were found in the plasma concentrations and total body clearance of amylobarbitone nor was there any alteration in the urinary elimination of 3-hydroxyamylobarbitone.

Determination of low cencentrations of the quaternary ammonium compound thiazinamium methylsulphate in plasma and urine.

A sensitive and selective method for the quantitative determination of the quaternary ammonium antiacetylcholine-compound thiazinamium methylsulphate (Multergan) in plasma and urine is described. The procedure is based on ion pair extraction of the compound with iodide as the counter ion. This is followed by gas chromatography using an alkali flame ionization detector. The detection limit is 2 ng ml-1 with a recovery of 88-0 +/- 6-2% from plasma, 91-4 +/- 4-6% from urine. The described method can also be applied to other quaternary ammonium compounds.

Determination of diethylcarbamazine in blood using gas chromatography with alkali flame ionization detection.

Abstract Diethylcarbamazine, 1-diethylcarbamyl-4-methylpiperazine, (DEC), is an antifilarial drug showing good microfilaricidal activity. Pharmacokinetic studies on this drug also are few probably due to lack of sufficient sensitivity of the methods reported in the literature for the determination of DEC concentration in biological fluids, viz. spectrophotometric methods [1–3] and the more recent improved gas chromatographic (GC) methods [4, 5]. The present report describes a GC procedure using an alkali flame ionization detector, for the quantitative determination of DEC in blood samples. The method can be used for measuring 50 ng of DEC (free base) and above in blood with a good degree of precision and accuracy. 1-Diethylcarbamyl-4-ethylpiperazine was used as the internal standard in the anayytical procedure.

Determination of phosphine by packed column gas chromatography with alkali flame ionisation detection

A method for the determination of phosphine using packed column isothermal gas chromatography has been developed and validated. The limit of detection is 0.01 ng ml–1 and response is linear over the ranges 0.1–1.0 and 2.5–25 ng ml–1. Reproducibility at 0.1 ng ml–1 was found to be 12.1% RSD. The method has been used to establish that phosphine is outgassed by newly fabricated semi-conductor devices containing phosphide compounds as dopants and is present in flatus of human origin.

Design and optimization of a novel type nitrogen-phosphorus detector for capillary gas chromatography

The design and optimization of a novel type alkali flame ionization detector (AFID) for capillary gas chromatography is presented. The design differs in that the alkali salt is continuously introduced, as a solution in water, into the detector by means of a liquid chromatographic syringe pump. This design permits continuous refreshment of the enhancement source and circumvents the need of source replacement, thereby eliminating detector response fatigue over time. Modification of an existing nitrogen-phosphorus detector (NPD) to allow direct introduction of the alkali salt into the detector will be described. Next, important operational parameters such as the location of introduction, type and concentration of the salt and the flow of the various detector gasses are optimized experimentally with regard to detector sensitivity, selectivity, minimum detectability and noise level. Moreover the linearity, reproducibility and stability of the detector are evaluated. It will be shown that the new detector design exhibits excellent response characteristics for phosphorus compounds which are comparable to or better than those observed with commercially available AFIDs or NPDs. Finally, the performance of the detector will be demonstrated by two environmental applications.

Simple Cleanup Procedure for Analysis of Buprofezin Residues and Its Metabolite in Crops by Gas Chromatography

Abstract An analytical method for determining residues of buprofezin (2-tert-butylimino-3-isopropyl-5-phenylperhydro- 1,3,5-thiadiazin-4-one) and its p-hydroxy metabolite (p-hydroxybuprofezin, one of its major metabolites in plants) in crops such as rice, citrus, and tomato was investigated. On the basis of the basicity of these compounds, a liquid–liquid partition, rather than column chromatography, was used for cleanup. Samples were extracted with acetone or methanol, and the concentrated extracts were partitioned between n-hexane and 1N HCI. After the aqueous layer was neutralized with 10N NaOH, the compounds were extracted with n-hexane, and the extract was analyzed with a gas-liquid chromatograph (GLC) equipped with an alkali flame ionization detector (AFID). p-Hydroxy- buprofezin was detected after acetylation with acetic anhydride–pyridine because its peak was broad and showed tailing on GLC. The limits of detection for buprofezin and p-hydroxybuprofezin were 0.005 ppm in hulled rice, citrus flesh, and tomato and 0.01 ppm in rice straw and citrus peel. Recoveries of both compounds fortified at 0.1 or 0.2 ppm were 75–97%.

Splitless injection of large volumes of aqueous samples: Further experience. Experiments on analyzing triazines by direct injection of drinking water

AbstractConditions were optimized for the introduction of large volumes of drinking water by splitless injection with vapor overflow, experimenting with the determination of triazines. No co‐solvent was added, and the maximum injection volume was 400 μl. A vapor outlet beyond a coated precolumn was used to discharge water vapors released belatedly from the packing. Using alkali flame ionization detection (AFID), detection limits were around 0.5 μg/l.

Tunable Selectivity of an Alkali Aerosol Flame Ionization Detector Towards Organobromine and Organoiodide Species for Gas Chromatography

Abstract The performance of a halogen selective aerosol alkali flame ionization detector (AFID) is presented. A constant delivery of desolvated alkali salt aerosol is introduced into the detector in the form of dual hydrogen gas flames. The problems of enhancement-source vaporization and contamination, which occur in fixed alkali salt versions, do not occur with the presented aerosol design. Detection limits range from 321 pgI/sec to 450 pgI/sec and 6.7 ngBr/sec to 15 ngBr/sec. Selectivity ratios were 103 gI/gC and 102 gBr/gC using an 100 ppm potassium chloride as the alkali salt solution.

Microanalysis of dialkylphosphorus metabolites of organophosphorus pesticides in human blood by capillary gas chromatography and by phosphorus-selective and ion trap detection

A procedure for the determination of dialkyphosphorus metabolites of organophosphorus pesticides in human blood has been worked out. Dimethyl and diethyl phosphates, phosphorothioates and phosphorodithioates, extracted with diethyl ether from plasma acidified with hydrochloric acid, were methylated with diazomethane and analysed by capillary gas chromatography with an alkali flame ionization detector and an ion trap detector. The extraction of metabolites was preceded by n-hexane extraction of parent organophosphorus pesticides without a negative effect on the efficiency of metabolite extraction. If plasma samples, containing 2 μ/ml of each metabolite, were not saturated with sodium chloride before extraction, only dialkyl phosphorothioates were recovered by more than 80%. The recoveries of other metabolites were less than 25%. The extraction of plasma samples saturated with sodium chloride resulted in higher recoveries of all metabolites. At concentrations ranging from 0.2 to 2.8 μg/ml the accumulation effeciencies (%±S.D.) of dimethyl and diethyl phosphorothioates were 92±20 and 97±11, and those of corresponding phosphorodithiotes 79±7 and 71±4. A significantly lower recovery (36±12%) was determined for dimethyl phosphate at concentrations in plasma below 2 μg/ml. The recovery of diethyl phosphate was dependent on the initial metabolite concentration in plasma being 31±5% at concentrations lower than 0.5 μg/ml, 51±12% at concentrations ranging from 0.7 to 1.7 μg/ml and 97±3% at concentrations at or above 2 μg/ml. Detection limits of metabolites in plasma using the phosphorus selective detector were 150 ng/ml for dimethyl phosphate and 50 ng/ml for other metabolites. Those values were for dialkyl phosphates and phophorothioates three to five times lower and for diakyl phosphorodithiotes even 30 times lower than detection limits achieved by the use of ion trap detector. The procedure was applied for the evidence and confirmation of human poisoning with organophosphorus pesticides.

The Performance of a Dual Alkali Aerosol Flame Ionization Detector for Gas Chromatography

Abstract The described alkali flame ionization detector (AFID) differs from other designs by introducing the alkali salt into the detector in the form of an aerosol. The preheated, desolvated alkali aerosol salt is introduced into a dual hydrogen gas flame assembly. This detector shows no evidence of fatigue due to the constant delivery of salt into the detector, compared to the fixed alkali supply found in other versions, which can be depleted by vaporization and become easily contaminated. This AFID design also allows for operation as an FID by implementing a simple pneumatic procedure. This paper deals with the performance and optimization of the detector using a dual alkali salt aerosol flame design for organonitrogen and organophosphorus compounds. Detection limits were 23.5 pgN/sec for alachlor, 185 pgN/sec for dinoseb, and 4.83 pgP/sec to 10.1 pgP/sec for various pesticides studied. Selectivity ratios are tunable to 6.6 × 106 gP/gC, 4.0 × 104 gN/gC and 2.3 × 103 gP/gN by establishing the appropriat...

Gas Chromatographic Determination of Caffeine in Beverages by Alkali Aerosol Flame Ionization Detection

The quantitative ability of the presented alkali flame ionization detector to determine the amount of caffeine in selected beverages is examined. A sample cleanup and concentration procedure is employed followed by gas chromatographic separation with alkali flame ionization detection. The amount of caffeine in 12-ounce containers of the beverages ranged from 35 mg to 60 mg. The linear response range of caffeine was observed to be 3.7 orders of magnitude.

The Evaluation of the Aerosol Alkali Flame Ionization Detector for High Performance Liquid Chromatography

The coupling of an aerosol alkali flame ionization detector with high performance liquid chromatography is described. The design of a heated interface allows vaporization of the liquid mobile phase, which prevents extinguishment of a detector flame. Detection limits ranging from 1.10 pg P/s to 17.0 pg P/s and 94.8 pg N/sec to 1890 pg N/s have been achieved. Selectivity ratios span greater than seven orders of magnitude for the organophosphorus probes and greater than six orders of magnitude for the organonitrogen compounds studied. The effect of detector void volume has also been considered; applications demonstrating detector selectivity are presented.

Alkali flame ionization detector for gas chromatography using an alkali salt aerosol as the enhancement source

A new design of an alkali flame ionization detector (AFID) is presented and differs from other configurations in that the enhancement source is introduced as an aerosol into a flame ionization detector (FID) rather than as a stationary solid bead positioned above a FID flame. This aerosol enters the detector as a hydrogen flame located perpendicular to the FID jet. Because the present design permits a constant and fresh supply of alkali salt to reach the detector, detector response does not fatigue over time. This AFID design also allows for operation as a FID by implementing a simple pneumatic procedure. This paper will deal with the performance and optimization of the detector in the phosphorous mode. The linear range for triethylphosphate exceeds four orders of magnitude. Selectivity ratios are in the four orders of magnitude range and detection limits for organophosphorus compounds studied ranged from 2.38 to 14.2 pg P/s.

Determination of ethylenethiourea in water samples by gas chromatography with alkali flame ionization detection and mass spectrometric confirmation

A gas chromatographic method with alkali flame ionization detection and mass spectrometric confirmation is described for the determination of ethylenethiourea (ETU) in water samples. The method is based on the extraction of ETU with dichloromethane in the presence of thiourea and sodium l-ascorbate. The limit of detection is less than 0.1 μg/l in water. The average recovery in groundwater is 71 %. Several hundred samples of groundwater and river water were analysed over a 2-year period.

Potential variability problems with the alkali flame ionization detector used in gas chromatography

Systematic gas chromatographic measurements on fourteen nitrogen- and three phosphorus-containing environmental pollutants revealed that potential variability problems may arise when using an alkali flame ionization detector. During an experimental period of 2 weeks the decrease in detector response turned out to be similar for homologous compounds, but different for compounds of diverse chemical classes. Although the absolute decrease in detector response may vary from bead to bead and, in addition, from one manufacturer to another, quantification appears to be feasable if this problem is taken into account by choosing internal standards of the same chemical class.

Analysis of deethyl‐ and deisopropylatrazine residues in drinking and ground water by chemical derivatization

AbstractA gas chromatographic method with alkali flame ionization detection is described for the determination of residue levels (0.1 μg/I and below) of deethylatrazine and deisopropylatrazine in drinking and ground water. Confirmation of the identities of the compounds is achieved by trifluoroacetylation, reaction conditions for which are presented.

Weed control and herbicide residues in onion following use of chlorpropham and cyanazine

AbstractA gas chromatographic method, using nitrogen‐phosphorus alkali flame ionization detection, is presented for the determination of residues of chlor‐propham and cyanazine in onion (Allium cepa L.). Recoveries of chlorpropham and cyanazine were 94 (±16)% and 84 (±7)% at the 100μg kg‐1 fortification level, and 97 (±8)% and 88 (±10)%, respectively, at 50μg kg‐1. Analysis of immature (whole plants) and mature (bulbs only) onions grown at four sites following a pre‐emergence application of chlorpropham at 6.0–6.7 kg ha‐1 and a subsequent post‐emergence application of a tank mixture of chlorpropham plus cyanazine at 4.5 and 1.1 kg ha‐1, respectively, resulted in no detectable residues of either herbicide. Weed control efficacy was evaluated for two consecutive years. The treatment demonstrated 88 % and 70 % broad‐leaved weed control 13 and 27 days after application, respectively, at the one site in Quebec.

The determination of the herbicide terbacil in asparagus spears by gas chromatography

In a 2-yr study, asparagus spears from established plantings at two sites in British Columbia and one site in Ontario were analyzed for terbacil residues following preemergence and early postemergence applications of terbacil at 0.6, 1.1 and 2.2 kg ha−1. Gas chromatographic determination of terbacil residues using N-specific alkali flame ionization detection indicated that at one site, maximum terbacil residues in the preemergence samples were 14 ± 3 μg kg−1 for the 2.2 kg ha−1 application rate, whereas maximum residues in the early postemergence samples for the 2.2 kg ha−1 application rate were 493 ± 250 μg kg−1 at a second site. Recoveries of terbacil from fortified asparagus tissue were 96 ± 19%, 87.2 ± 11.9% and 83.3 ± 7.8% at 10, 50 and 100 μg kg−1, respectively. Key words: Asparagus officinalis L., terbacil, residues, gas chromatography, asparagus